Renault will switch Red Bull on to its newest specification of alternator for the championship decider in Brazil following Mark Webber's failure in the United States Grand Prix.

Webber suffered Red Bull's third alternator failure in a race this year at Austin, dropping him out of third position.

That problem prompted concerns from the team about that area of the car, which has left engine partner Renault in no doubt that Red Bull must switch to the newer spec for this weekend's Interlagos showdown.

Renault's head of trackside operations Remi Taffin told AUTOSPORT about the plans for Brazil: "It is very simple. We go for the new spec. It has passed all the tests."

Red Bull elected not to use the newer specification, which was raced by other Renault teams, because it felt safer using the older specification that had so far proved trouble-free.

When asked why that decision had been made if the newer units had passed all reliability tests, Taffin said: "Because they are human beings and at some point as humans they have some feelings.

"It was a common decision, so we put everything on the table and we decided altogether we should go that way. We had everything to fit either the old or new design.

"But the feeling was generally that there is some sense to keep on using something that we have known for years with low mileage and stuff like that, even if we had a new solution that we knew had gone through all the tests.

"Maybe it is a bit more difficult to understand, but put yourself in the situation where you have to make a decision.

"Sometimes you go into a shop and there are two different things and your head says you should buy this one but your heart says you should buy the other one."

Taffin added that the fact that Renault's other teams had successfully used the revised newer specification of alternator last weekend meant that Red Bull should have no concerns about its reliability for Brazil.

"This is the first Sunday it has been used, but now we are up to 2000km on a few items with track and dyno testing, so there is nothing we would do more on this item before we fit it on the car."